What is the ruling on uttering the second divorce pronouncement: "I have divorced you definitively," and does a second divorce take effect by it, bearing in mind that the intention behind it was to affirm the first divorce and not to initiate a new one, and reconciliation took place hours later?

As long as you intended to inform your wife of the divorce and did not intend to initiate a new divorce, then only one divorce has occurred. A revocably divorced woman should not leave her husband's house, and it is not permissible for her husband to expel her from it until her waiting period ('iddah) ends.